The present invention disclosed herein relates to a dip molded product having excellent tensile strength, elongation, and touch, a preparation method thereof, a composition for dip molding for preparing the dip molded product, and a latex for dip molding used in the composition for dip molding.
A natural rubber latex has typically been used as a raw material for dip molded products such as rubber gloves, but recently, there are limitations in that a protein in the natural rubber latex causes rash, itchiness, or common cold by allergic reactions occurred when the protein is in contact with human skin. Accordingly, a carboxylated acrylonitrile-butadiene-based copolymer latex, a synthetic rubber latex without including a protein, receives attention and the use amount thereof tends to increase.
In addition, high levels of physical properties, such as tensile strength, elongation, and touch, are recently required for a dip molded product obtained by using a typical composition for dip molding, while high qualities are needed with respect to a latex for dip molding according to the increase in the use amount thereof.
When the stability of a composition for dip molding is maintained, tensile strength, elongation, and touch of a dip molded product may be improved. When the stability of the composition for dip molding is not maintained, it may cause significant loss to a manufacturer of dip molded products because tensile strength, elongation, and touch of the dip molded products significantly decrease as well as the occurrence of limitations, such as flow marks and pinholes of the dip molded products. The foregoing stability of the composition for dip molding becomes more important in order to obtain high qualities of the dip molded product and may be an important factor in determining productivity of the dip molded product.
In many cases, the stability of the composition for dip molding commonly depends on a latex for dip molding. A latex used in the composition for dip molding is generally a carboxylated acrylonitrile-butadiene-based latex and the stability thereof is maintained by a carboxylic group and an emulsifier on a surface thereof. Typically, the carboxylic group may be obtained by using an ethylenically unsaturated acid as a copolymerizable monomer and the carboxylic group may increase stability by being fixed on a latex surface. However, in many cases, the carboxylic group may not provide sufficient chemical stability in a pH range of 9 to 12, a pH range of a typical composition for dip molding.
Therefore, an emulsifier is used for the chemical stability of the composition. Although the emulsifiers may differ according to a functional group thereof, the stability may be increased by using a generally used anionic emulsifier having a functional group, such as sulfate and sulfonate, or an ethylene oxide-based non-ionic emulsifier. However, since the emulsifier, different from the carboxylic group, is not fixed but absorbed on a latex, there are limitations in that efficiency for the stability may decrease by desorption occurred during the application of mechanical shear and the generation of gas bubbles may be severe.
Also, a scale problem may be generated as one of great difficulties in preparation of the latex for dip molding. A large amount of scales may be generated in a reactor or on an agitator during the preparation of the latex according to characteristics thereof. Since the scales may cause a lot of problems such as non-uniformity of physical properties during a continuous process by acting as an impurity during a subsequent process and great time and efforts may be required to remove the scales, the scales may greatly influence on the reduction of productivity.
Different from the scales formed in the reactor, coagulums may exist in a suspension and are filtered through screening after the completion of polymerization and during the preparation of the composition for dip molding. Product management may be difficult because a lot of time and costs are used for the filtration thereof and qualities of a dip molded product may deteriorate because fine agglomerates may appear in the dip molded product during dip molding.